APP and Alzheimer disease: To explore the potential of fE/I as a biomarker of network E/I imbalance in early stages of Alzheimer's disease, we computed fE/I from LFP signals recorded during quiet wakefulness in the HC and PTC (Fig. 1A, i) of freely behaving APP/PS1 mice between 3 and up to and including 11 months of age (hereafter referred to as ‘between 3 and 11 months of age’; Fig. 1A, ii) and compared the results to those from WT littermates.